United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S2-88/058 Jan. 1989
EPA Project Summary
Granular Activated Carbon
Adsorption With On-Site
Infrared Furnace Reactivation
Wayne E. Koffskey and Benjamin W. Lykins, Jr.
The costs associated with the design,
construction, operation, and mainte-
nance of a 3 million gallons per day
(mgd) post-treatment granular activated
carbon (GAC) adsorption and reactiva-
tion system were evaluated over a 2.4 yr
operational period. The adsorption sys-
tem consisted of three 1-mgd GAC pres-
sure contactors designed with a nozzled
plenum plate underdrain, each contain-
ing 1,857 ft3 of granular activated car-
bon. The reactivation system was com-
prised of a microprocessor-controlled
Shirco infrared reactivation furnace,
three GAC storage tanks, and a water
slurry GAC transport system. The over-
all design and construction costs were
$2.25 million while operation and main-
tenance costs,excluding amortized
capital costs, were determined to be 20
cents/lb of reactivated GAC or 14 cents/
1,000 gal of treated water.
The use-related GAC morphological
changes, GAC adsorption performance,
and GAC loss were evaluated for four
GAC lots over 4 to 5 reactivation cycles.
While some variability in GAC morphol-
ogy was indicated, the GAC organics
loading data, obtained for various GAC
lots over successive reactivation
cycles, Indicated that the adsorption
performance of the reactivated GAC was
equal to or greater than that of virgin
GAC for all parameters monitored. The
GAC loss observed during reactivation
averaged 8.6% and was comprised of
7.1% reactivation loss and 1.5% trans-
port loss.
The effluent streams of the infrared
reactivation furnace were examined for
the presence of polychlorinated diben-
zodioxins and polychlorinated diben-
zofurans. While trace levels of some of
these substances were observed, a risk
assessment indicated a maximum life-
time risk of three in 1 billion for the
existing facility.
Another objective of this research ef-
fort was to obtain bacteriological infor-
mation at the surface of the GAC within
the adsorption system and in the efflu-
ent of the adsorption system. The GAC
filter effluent contained a mean hetero-
trophic plate count (HPC) of 3,137 col-
ony forming units (CFU)/mL, which was
comprised of approximately 50%
Pseudomonas and 25% gram positive
bacteria. While the HPC on the GAC
surface was considerably higher with a
geometric mean of 3.5 x 106 CFU/mL,
similar bacterial species were observed.
This Project Summary was developed
by EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce
key findings of the research project that
is fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
The Mississippi River along with its tribu-
taries drains nearly two-thirds of the conti-
nental United States and is used as a drink-
ing water source by many of the cities
located along its banks. The waters of the
Mississippi River and its tributaries also
serve as the receivers of vast quantities of
industrial and municipal wastes as well as
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agricultural run-off, resulting in the occur-
rence of trace levels of synthetic organic
chemicals in this drinking water source. Of
equal or sometimes greater concern are
those naturally occurring substances that
form halogenated by-products during the
disinfection process.
Other water sources, besides the Missis-
sippi, also contain many of these contami-
nants and several drinking water utilities are
potentially facing the implementation of
GAG adsorption technology to meet im-
pending federal and state regulations.
While previous studies have demonstrated
the effectiveness of GAG adsorption for
reducing the concentrations of organic
contaminants in drinking water, only a few
of these studies have evaluated the eco-
nomics of full-scale GAG adsorption with
on-site reactivation.
Therefore, objectives for this study were
developed to fully document the use of
GAG to treat a river water source. These ob-
jectives consisted of the following:
• To examine the use-related morpho-
logical changes in GAG resulting from
reactivation.
• To determine the effects of several
thermal reactivation cycles on GAG
adsorption performance.
• To perform a material balance on
GAG for several thermal reactivation
cycles in order to determine the vol-
ume of GAG lost across the reactiva-
tion furnace and in the GAG transport
system.
• To accumulate and evaluate cost in-
formation forthe design, construction,
operation, and maintenance of a full-
scale GAG facility with on-site thermal
reactivation.
• To determine the presence and sig-
nificance of polychlorinated dibenzo-
dioxins and polychlorinated diben-
zofurans in the effluent streams of the
infrared reactivation furnace.
• To obtain bacteriological information
at the surface of the carbon within the
GAG system and in the effluent water
of the system.
Three 1-mgd GAG pressure filters and a
215 Ib/hr infrared reactivation furnace were
used during the operational period from
March 1985 through February 1988. Mor-
phological data and loading data for the
various parameters of interest as well as
bacteriological data were collected for vir-
gin GAG through the fifth reactivation. Volu-
metric GAG losses as well as operational
and maintenance costs were determined
for five reactivations of four GAG lots total-
ing approximately 38,000 ft3 (966,000 Ib).
Polychlorinated dibenzodioxins and poly-
chlorinated dibenzofuran analyses were
performed on the furnace effluent streams
along with a risk assessment of the levels
found.
Treatment Plant Configuration
Conventional Treatment
Mississippi River raw water is pumped to
the East Jefferson Parish water treatment
plant where fluosilicic acid (up to 4 mg/L) is
added followed by powdered activated
carbon (2 mg/L) and cationic polyelectrolyte
polymers (up to 8 mg/L) prior to clarification.
After clarification, am monia gas is added to
the process stream followed immediately
by chlorine at a chlorine to ammonia ratio of
3:1 prior to sand filtration. After sand filtra-
tion (2 gpm/ft2), zinc-sodiumhexameta-
phosphate (1 mg/L) was added. Prior to
entering the distribution system, aportion of
the finished water was diverted to the GAG
adsorption and reactivation facility.
GAC Research Plant
Conventional treatment plant finished
water was pumped into one of the three 1 -
mgd GAC contactors. Operation of the GAC
contactors (20 min EBCT each) was sched-
uled so that reactivation of exhausted car-
bon could be done without interrupting GAC
adsorption studies. Each of the GAC con-
tactors was designed to withstand a differ-
ential pressure of 60 lb/inz (psi) with water
flowing upward for backwashing and 70 psi
in a downward direction. Abeam supported
underdrain contained 212 stainless steel
filter nozzles for passage of the GAC effh
ent.
A slurry system was used to transport
GAC. Four-inch pipe bent to a minimum
radius of 2 ft was used for all transport lines
except for those between the furnace
quench tank and the reactivated GAC tank.
These lines were constructed of 1.25-in.
pipe to a radius of 1.5 ft.
Thermal reactivation of exhausted GAC
by the Shirco infrared reactivation system
consisted of three sequential steps: drying,
volatilization and pyrolysis of adsorbed
organics, and reactivation with flue gas and
steam. Exhausted GAC was fed through a
rotary valve into the furnace feedhopper
and into the furnace by a dewatering screw.
From the feed chute in the furnace, GAC
was drawn off by a woven wirebelt and
leveled to a depth of 0.75 in. Reactivation
was accomplished by glowbars placed
above the belt.
GAC Performance
Organic Chemicals
Organic chemical analyses performed
during the study included: total organic
carbon (TOG), total organic halide (TOX),
volatile organics (VOA), capillary gas chro-
matography (CGC) of solvent extractablt**
with electron capture and flame ionizatio^
detection, and gas chromatography/mass
spectrometry (GC/MS) of both volatile or-
ganics and solvent extractables. Extensive
data were collected from these analyses.
Table 1. Average GAC Performance For A Reactivation Cycle Of 3 Months
Parameter
TOO, mg/L
TOX, ng/L
TOX-FP", fig/L
TTHM, pg/L
TTHM-FP', ng/L
TFIC+, ng/L
TECC*, ng/L
Total Alkylbenzenes, ng/L
Total Alkanes, ng/L
Total Phthalates, ng/L
Total PNAHs®, ng/L
Total Nitrobenzenes, ng/L
Total CHIsa, ng/L
Influent
3.5
114
500
3.8
250
3.6
0.6
251
144
142
156
59
129
Effluent
1.2
9
128
0.4
70
1.2
0.1
89
109
78
32
13
6
Percent
Removal
67
92
74
89
72
67
89
65
24
45
79
78
95
' FP - formation potential
+ TFIC - total flame ionization concentration
* TECC - total electron capture concentration
® PNAHs - polynudear aromatic hydrocarbons
* CHIs - chlorinated hydrocarbon insecticides
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^Therefore, GAG performance for a react iva-
n cycle of 3 mo was selected as atypical
»**ample. This data as presented in Table 1
shows that GAG with a 3-mo reactivation
cycle removed from 24% to 95%, by aver-
age, of the groups of compounds evalu-
ated.
Bacteriological
Bacteriological parameters monitored
included heterotrophic plate count (HPC),
total coliforms, and speciation of gram
negative bacteria from the HPC analyses.
The geometric mean HPC of the influent
water to the GAG facility was 19 CFU/mL
with an observed maximum of 330 CFU/mL.
The geometric mean increased to 3,137
CFU/mL in the effluent of the GAC facility
with an observed maximum of 1.6 x 105
CFU/mL. This level of biological activity
produced a dissolved oxygen reduction of
3.9 mg/L across the GAC contactors from
an average influent level of 8.6 mg/L to an
average effluent level of 4.7 mg/L.
Total coliforms were detected in the influ-
ent to the GAC facility in 7 samples with a
maximum of 5 CFU/100 mL and a non-zero
average of 2 CFU/100 mL. In the GAC
effluent, total coliforms were observed in 21
samples with a non-zero average of 1 CPU/
100 mL and a maximum of 7 CFU/100 mL.
-Disinfection of the GAC effluent reduced
e HPC and coliforms to acceptable levels.
Of the 19 CFU/mL HPC present in the
influent water, about 80% were gram posi-
tive bacteria occurring in 93% of the
samples while Pseudomonas accounted
for 7% occurring in approximately 20% of
the samples. In the GAC plant effluent, the
geometric mean of the HPC of 3,137 CFU/
mL was composed of approximately 49%
Pseudomonas in about 95% of the samples
and 25% gram positive bacteria in 84% of
the samples.
The level of HPC on the surface of the
GAC was considerably higher than the
plant effluent with a geometric mean of 3.5
x 106 CFU/mL. Essentially the same bacte-
riological trend observed for the plant efflu-
ent was also found on the surface of the
GAC within each contactor. The number of
unknown bacteria did not change signifi-
cantly across the GAC beds but the number
of picked colonies that did not regrow on
nutrient agar increased from 3% to 13%.
GAC Reactivation
Morphology
Analyses were performed on both spent
and reactivated GAC to determine reactiva-
tion quality and to measure any physical
hanges in the GAC which may result from
apeated reactivations. These analyses
consisted of apparent density, percent ash,
iodine number, sieve (effective size, uni-
formity, coefficient, and mean particle di-
ameter), molasses number, abrasion num-
ber, volatile matter, phenol number, percent
moisture, BET surface area, and pore size
distribution.
Generally, the reactivated carbon was
comparable to virgin GAC. Some variations
were observed, as shown in Table 2. These
variations are suspected to have occurred
from non-representative samples. From all
indications, however, the origin GAC lot
within each contactor can be continually
recycled without any performance deterio-
ration until it is eventually replaced through
attrition by makeup GAC.
Losses
One of the most important economic fac-
tors in determining the feasibility on on-site
reactivation is the amount of GAC loss
associated with both GAC transport and
GAC reactivation. In order to accurately
determine losses, each GAC contactor and
storage tank had to be calibrated. After
calibration, GAC volume measurements
were performed on each vessel after back-
washing from 5 to 10 min and draining for
approximately 40 min. The contactors were
backwashed at 900 gpm (8.2 gpm/ft2) while
the flow rate used for the storage tanks was
300 gpm (2.7 gpm/ft2) because of their lack
of backwash freeboard. Each pressurized
GAC contactor had four measuring ports
while each storage vessel had ten measur-
ing ports. The backwash/drain/measure
sequence was repeated a minimum of three
times until the average of three GAC vol-
ume measurements were within 0.05 ft of
each other. This resulted in the GAC vol-
umes being within 5.5 ft3 of one another or
0.3% of a full contactor load of 1,857 ft3. The
average total loss was 8.6% with 7.1 % loss
occurring during reactivation and 1.5%
during GAC transport.
Byproducts
Each effluent stream of the reactivation
furnace was sampled for polychlorinated
dibenzodioxins (PCDDs) and polychlori-
nated dibenzofurans (PCDFs) during reac-
tivation of virgin and exhausted GAC. No
PCDDs or PCDFs were detected during
reactivation of virgin GAC indicating that the
GAC did not produce or contain these
compounds. However, during the reactiva-
tion of exhausted GAC, PCDDs and PCDFs
were observed in the stack gas of the reac-
tivation furnace.
Concentrations for each isomer detected
were multiplied by their respective 2,3,7,8-
tetrachlorodibenzodioxin (TCDD) toxic
equivalence factor to determine 2,3,7,8-
TCDD equivalent concentrations. The total
average 2,3,7,8-TCDD equivalent concen-
tration was 0.68 ng/dscm. At agas flow rate
of approximately 200 dscm and a 7,000 hr
operating year, an annual emission of 100
ug/yr resulted. The associated maximum
lifetime risk for this level of emission was 3
x 10'9 (three in 1 billion).
In addition to the PCDD and PCDF analy-
ses, scrubber water, quench tank water,
spent GAC, and reactivated GAC were also
analyzed for the presence of halogenated
and nonhalogenatedorganics and other by-
products using liquid extraction and soxhlet
extraction techniques. The organic content
of the scrubber effluent water was generally
lower than that of the GAC plant influent
water. WhileTOC showed essentially no
change from the influent water, TOX exhib-
ited an average reduction of 42% from 118
ng/L to 69 ng/L. Similarly, the total amount of
volatile organics measured was reduced
48% from 6.7 |ig/L to 3.2 ng/L. Pentane
extractable hydrocarbons and chlorinated
hydrocarbon insecticides also exhibited
general reductions of 37% with TFIC re-
duced from 4.2 ng/L to 2.7 ng/L and TECC
reduced from 0.50 ng/L to0.31ng/L. For the
quench tank effluent water, general reduc-
Table 2. Reactivated GAC Morphology Over Successive Thermal Reactivations
Reactivation Number
Virgin
Apparent Density (g/mL)
Iodine Number (mg/g)
Molasses Number
Effective Size (mm)
Uniformity Coefficient
Mean Particle Diameter (mm)
Abrasion Number
Ash (%)
BET Surface Area (rrf/g)
AWWA Phenol (g/100g)
Volatile Matter (%)
0.54
872
237
0.80
1.72
1.2
77.1
8.9
892
16.7
5.6
0.49
1070
303
NA-
NA'
0.56
71.0
11.4
1066
22.1
5.7
0.54
897
224
0.57
1.86
1.12
74.4
10.0
777
18.5
6.8
0.57
777
220
0.69
1.66
1.11
77.0
8.7
714
15.6
NA'
0.56
864
228
0.66
1.69
1.06
76.2
9.1
1183
13.6
26.2
0.57
846
235
0.67
1.76
1.13
70.2
8.7
751
16.5
4.0
'NA - not analyzed
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tions were observed in the organic content
of the GAG plant influent water.
Infrared reactivation removed 90% of the
organics adsorbed on the GAG, based on
chloroform soxhlet extraction residues. For
the 3-mo reactivation cycles, chloroform
residues were reduced from an average of
1.79 g/kg of GAG to 0.17 g/kg of GAG. The
chloroform extracts were also analyzed for
specific halogenated and nonhalogenated
semivolatile organics. The results of these
analyses, which were summarized by TFIC
and TECC, indicated that there was only a
small difference between spent GAG and
reactivated GAG for those semivolatiles
analyzed. The TFIC was reduced by an
average of 27% from 0.059 g/kg to 0.043 g/
kg while the TECC was reduced by only 9%
from 0.0079 g/kg to 0.0072 g/kg. Other sub-
stances, such as PNAHs, were formed
during the reactivation process.
Costs
The average operation and maintenance
(O&M) GAG transport and reactivation cost
was 20.4 cents/lb. The O&M GAG transport
cost was 1.6 cents/lb and was comprised of
1.1 cents/lb for GAG loss, 0.3 cents/lb for
operating labor, and 0.2 cents/lb for water.
The cost associated with GAC loss was
determined using an average transport loss
of 1.5% while that for water consumption
was derived from an average figure of
372,000 gal/reactivation, which included
three backwashes per vessel for volume
measurement. The operating labor cost for
GAC transport was estimated on 12.5 hr/
reactivation and included 2.5 hr of transport
time, 0.5 hr for paperwork, and 9.5 hr for
drain and volume measurements per ves-
sel.
The O&M GAC reactivation cost was esti-
mated at 18.8 cents/lb and included 5.8
cents/lb for electricity, 5.3 cents/lb for GAC
loss, 3.6 cents/lb for maintenance labor, 1.7
cents/lb for maintenance material, 1.5
cents/lb for operating labor, 0.7 cents/lb for
water, and 0.2 cents/lb for laboratory. The
cost of electricity was based on an average
usage of 46,508 kwh/reactivation deter-
mined over 11 reactivations with the after-
burner in operation. The cost for GAC loss
was determined using an average 7.1%
loss per reactivation. The cost of operating
labor was estimated at 63 hr/reactivation,
which included an estimated 15 min/hrfor
taking readings and observing system
operation over an average period of 10.5
days.
The cost of maintenance labor was based
on the actual maintenance hours used for
the last 15 reactivations, which averaged
136 hr/reactivation. A total maintenance
material cost of $16,876 incurred over 20
reactivations along with an average reacti-
vated GAC volume of 1,789 ft3 was used to
determine the O&M maintenance material
cost for GAC reactivation. The figure of 1.7
cents/lb does not reflect any materials re-
placed under warranty, the cost of the even-
tual repair or replacement of the corroding
duct between the furnace and the after-
burner, or the cost of eventual belt replace-
ment at approximately $10,000. The cost
for water consumption was derived using
the average water consumption over 15
reactivations of 1,280,500 gal/reactivation.
The overall O&M cost for the GAC adsorp-
tion and reactivation facility for a 3-mo reac-
tivation cycle with a 20 min EBCT was
estimated at 13.7 cents/1,000 gal. This cost
was comprised of 2.8 cents/1,000 gal for
GAC contactor operation, 0.9 cents/1,000
gal for GAC transport, and 10.0 cents/1,000
gal for GAC reactivation. The O&M cost for
the GAC contactors was further broken
down to 2.0 cents/1,000 gal for electricity,
0.6 cents/1,000 gal for operation labor, and
0.2 cents/1,000 gal for laboratory.
Conclusions
• Loading curves for all parameters
monitored indicated that reactivated
GAC adsorption performance was
equal to or greater than that of virgin
GAC.
• While coliforms were detected in both
the influent and the effluent of the
GAC contactors, the levels found
were not statistically different indicat-
ing essentially no change in coliform
density across the GAC contactors.
• The overall magnitude of morphologi-
cal changes observed after repeated
reactivations was minimal indicating
that the original GAC lot within each
contactor can be continually recycled
until it is eventually replaced through
attrition by make-up GAC.
• The average total GAC loss observed
for the reactivation and transport of 20
GAC lots was 8.6%. This total GAC
loss was comprised of 7.1% reactiva-
tion loss across the infrared reactiva-
tion furnace and 1.5% GAC transport
loss.
• While some polychlorinated dibenzo-
dioxin and dibenzofuran isomers
were observed in the infrared reacti-
vation furnace stack gas equivalent to
a 2,3,7,8-tetrachlorodibenzodioxin
emission of 0.68 ng/dscm, the lifetime
risk level assessed for this level of
emission at the Jefferson Parish site
was 3 X 10'9 or three in 1 billion.
• No polychlorinated dibenzodioxins or
dibenzofurans were found in any of
the process streams of the reactiva-
tion furnace during the reactivation of
virgin GAC indicating that these sub-
stances originated from the organic
substances and chlorine species ad-
sorbed onto the spent GAC as op-
posed to being inherent in the infrared
reactivation process.
•All plumbing inside the contactors and
storage vessels should be made of
316L stainless steel to prevent an
eventual failure from the rapid corro-
sion produced by GAC fines on car-
bon steel.
• The average O&M GAC transport and
reactivation cost was 20.4 cents/lb.
Transport cost was 1.6 cents/lb and
reactivation cost was 18.8 cents/lb.
Overall O&M cost for a 3-mo reactiva-
tion cycle with a 20 min EBCT was
13.7 cents/1,000 gal.
The full report was submitted in fulfillment of
Cooperative Agreement No. CS806925 by
the Jefferson Parish, Louisiana Depart-
ment of Public Utilities under the sponsor-
ship of the U.S. Environmental Protection
Agency.
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Wayne E. Koffskey is with the Jefferson Parish, Louisiana Department of Public
Utilities, Jefferson Parish, LA 70121.
Benjamin W. Lykins, Jr. is the EPA Project Officer (see below).
The comphte report, entitled "Granular Activated Carbon Adsorption With On-Site
Infrared Furnace Reactivation" (Order no. PB89-110 134/AS; Cost: $19.95, cost
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
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Penalty for Private Use $300
EPA/600/S2-88/058
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